Medical diagnostic imaging is widely used for the examination of body cavities. A prerequisite for the imaging of body cavities is the instillation of a fluid in order to obtain a fluid-filled cavity. In these fluid-filled cavities, the fluid has two functions: (1) to open up the cavity from its “collapsed” state (distension) and (2) to enhance the contrast of the image of the body cavity. Conventionally, water or watery fluids are used for distension and contrast imaging. In intervention cardiology or radiology, kidneys, liver, intestines, this is sometimes combined with the generation of bubbles, to further increase contrast in the veins. Examples of so-called microbubbles are given by U.S. Pat. No. 4,681,119. Disadvantageously, the gas contained in these watery fluids disappears almost instantaneously, and would thus require continuous replenishment during imaging. However, this is often not very convenient for the patient.
On the other hand, EP 1,793,860 provides a solution to overcome the inconveniences and discomfort caused by leakage of aqueous solutions while imaging. Thereto, it discloses a gel composition having a viscosity of between 2000 and 4000 mPa·sec, containing cellulose or cellulose derivative. The composition may be used for the imaging of any body cavity. The commercially available ExEm® falls within the scope of EP 1,793,860. The gel is stable and does not contain any particles or micro bubbles. In fact, these are considered to give rise to artifacts. Where excellent results are reported for the ExEm® e.g. when imaging the content of the uterine cavity, the composition appears not particularly suited when performing a patency test, i.e. to examine the fallopian tubes for blockage, either desired or undesired. It requires considerable pressure (causing pain to the patient) to insert the gel into the tubes, and even then it appears not feasible. In that respect, it is noted that it is of the essence that any difficulties experienced by inserting distenting media into the tubes should not be mistaken for real (permanent) blockage of the fallopian tubes.
Previously, an ultrasound contrast agent ECHOVIST was marketed by Schering AG, which agent consisted of a suspension of micron-sized air bubbles, formed upon reconstitution of specially formulated galactose granules with an aqueous galactose solution. Amongst other drawbacks, its ingredients and tedious preparation made it a costly tool to visualize the fallopian tubes. It appears no longer available on the market.
Outside the field of the invention, US 2003/0206862 describes a contrast medium for intraveous administration, wherein small gas bubbles are introduced into the bloodstream. The ultrasound contast medium contains solid polyoxyethylene-660-12-hydroxystearate particles. It goes without saying that the intravenous applications taught in US 2003/0206862 put less constraints to the use of solid particles, while the skilled person in the field of sterilization and fertility investigations is searching for particle-free, embryotoxic-free solutions. Adhesion is to be prevented at all cost.
There is thus a need in the art for a simplified, cost-effective agent for imaging of fallopian tubes which is easy-to-handle, enables high quality images without jeopardising the health of the patient and without loss of echogenicity during imaging.